:
A "gold filled" watch case is constructed like a
: sandwich. The case has a thin layer of gold (usually 10kt or
: 14kt) over a base metal layer, then followed by another thin
: layer of gold. I believe by law, the gold layers must comprise a
: minimum of 1/20 of the thickness of the case. The case backs are
: usually made of stainless steel in watches from the 50's thru
: today. Gold filled cases are subject to "wear through"
: or "brassing" where the top layer of gold fill wears
: away due friction or deep scratches, exposing the non-gold base
: metal.
: Plated gold, as opposed to gold fill cases, uses a very, very thin
: layer of gold which is electroplated (older watches) or
: "PVD" (physical vapor deposit, I think).
: Electroplating is a cheaper, less elegant method as opposed to
: gold filled.
: A solid gold case is entirely made of gold (no base metal layer as
: in "gold filled" cases), usually 10kt, 14kt or 18kt,
: including the case back. In most of Europe, solid gold watch
: cases are made of 18kt gold due to laws which don't consider
: less than 18kt gold as being "real gold". However,
: even 18kt solid gold is not totally "pure" solid gold
: since "pure" gold (without a mixture of alloys) is
: referred to as 24kt gold. Therefore 18kt gold is 75% gold
: (18/24) with the remaining 25% composition being a mix of
: various alloys such as copper, silver or nickel. A red gold
: case's alloy mixture tends to have more copper in it (giving the
: pink or reddish hue to the gold) while white gold has a higher
: alloy mix of silver, I believe. A 10kt gold case is 10/24, or
: just 42.7% "pure gold" while 14kt is 14/24, or 58.3%
: "pure gold". 24kt solid gold is not used in watch
: cases (or jewelry) because it is way too soft and too prone to
: scratches or damage. The one advantage to 10kt or 14kt is that
: it is less prone to scratches since the alloy mix makes its
: composition harder. I'm not a jeweler so please excuse my
: layman's terms. i learned the above from various sources
: including Rene Rondeau's book on Hamilton Wristwatches (now out
: of print). I hope tyhis makes sense to you!
: Steve
Well most of that is correct. The law states that 1/20 of the total weight not thickness needs to be gold to be considered GF. The gold filling process is not technically a plating process. The gold is put on with heat and pressure so it fuses to the base metal, usually brass. This process yields a layer that is ~100 times thicker than the electroplating process. GF is not technically a plating process since there is no electrolytic process or an autocatalytic process that takes place...it's physically fused to the base metal.
Sometimes gold plating is also labelled as HGP if the plating layer is 2.5microns. Normal GP layers are .5. Hope this helps
